Twin Comanche: Cosmetic or major issue?

[David Wainland]

I looked over a PA30B my partners and I are considering the other day and spotted several areas of what appeared to be filiform corrosion, a few rusty linkages on the gear, and some other small but noticeable issues. There was also a lot of peeling paint around wheel wells, though the zinc seemed to be holding up under it. Even where it was not zinc coated, I saw very little corrosion.

I know that ultimately a good pre-buy is the answer to "are these issues major" but was curious if anyone on the board had an opinion before I invest time and money into a pre-buy. Any thoughts are greatly appreciated; I know there is a limit as to what you can see with pictures and that any information is friendly advice only--not professional opinions! I just don't know Comanches well and want to get some help getting a feel for what I'm looking at!

A few pictures attached.

[Kristin Winter]

Hard to tell much from the pictures. I can't tell anything about the first two. The surface corrosion under the wings is worse than I generally see when doing pre-purchase consulting. It is eminently repairable, but I am guessing that this aircraft has been spending time in marine environment, likely a salty one. I am guessing that there are quite a few of those.

[David Wainland]

Yes... from 2001 to 2008 it was based in the greater Los Angeles Area. Numerous log entries in LA, and a few from San Diego area during that time.

[N3322G]

I'd also guess there is some damage history - which is fine if the repairs have been done by a reputable shop. I guess that becasue of the differing zinc chromate colors and uncoated rivets. If this is well documented in the logs it is one thing but if not, well, higher risk.

[Kristin Winter]

LA and SD area can vary greatly depending on which airports they were actually on. IMX, on the west coast, the need to be quite a bit closer to the ocean than on the Atlantic or the Gulf. The reason is likely due to the much lower humidity out on the west coast. Because the water is colder, it does not pump as much moisture into the atmosphere out here.

It is prudent when looking all over the country for a plane, to have a logbook review done before embarking on a full pre-purchase inspection, especially when a significant amount of travel might be involved. In four or five hours someone who is familiar with the aircraft and familiar with analyzing logbooks can tell you a lot about the plane. Aside from examining the AD status, you can get a pretty good idea of how the aircraft was maintained, where it was, and how it has been used. One twin whose logs I recently looked at showed an entry for a repair to the wings and referenced an engineering report. That an the 337 showed the wing structure to have been damaged at the point where the main landing gear was attached. The aircraft had also had a sudden stoppage of the engines. The buyer assumed they were related. In fact, the landing gear collapsed, just a couple of hours after it was returned to service after the repair if the wings. This told me that there were two different events. The first was likely a very hard landing and the second was likely caused because the landing gear was improperly installed or rigged. The interested buyer elected not to have me travel to do the pre-buy, given that he was interested in a plane to fly for 5 or so years and then sell. He was reasonably afraid that the damage history was too recent and there were too many risks for a shorter term ownership. If it was going to be your bird for 20-30 years or more, you can amortize surprises and damage history's affect on the value fades with time.

[David Wainland]

Kristin, sent you a PM regarding specific questions about pre-buy services.

In general, how are Twin Comanche's aging. I've seen several in the 7000 to 10000 hour range on the market. My general experience has been inactivity and corrosion are worse than high hours, but I'm a novice on the PA30! I have flown 20000 hour 172s, and my understanding is the Comanche frame is more robust.

Attaching another picture... this is a scary one from a gear well... probably the ugliest spot on the plane. Hard for me to tell exactly what is dirt versus nasty paint vs old lubricant vs corrosion!

[Kristin Winter]

David,

I saw the PM and replied with email and phone as well as answering your question about charges.

Wheel wells are usually the ugliest spot, and that one is particularly in need of TLC.

I know that Twin Comanches have been used for clouding seeding with over 10K hours. I figure if they can hold up to that kind of hard flying, they are good for a long time after that. The Comanches are definitely more rugged than a C-172.

[Charles Schefer]

My 2-cents FWIW... Agree with the other responses. Good catch by Pat regarding the different zinc chromate coloring (darker green than factory) indicating something was redone. I also note the rivets thru that area are unpainted furthering the impression. I agree it is difficult to really assess just from pics.

Regarding the landing gear. Looks like the gear wells are painted over but some paint is peeling leaving areas of the original zinc chromate showing. I believe from the factory they were just zinc chromate. The corrosion in the pic is on the factory push-pull rod. If this were my plane I'd plan to replace them with the Webco teflon lined units. Also the gear wiring looks original and that might need replacing depending on condition. When were the gear ADs complied with? Specifically AD 77-13-21 "Prevent Landing Gear Collapse (Components Wear Limits) Para (a-c) and also AD 97-01-01 R1 "Main Gear Sidebrace Stud". I'd also have someone with experience take a look at the condition of the gear transmission and check the retraction loads.

I cannot emphasize enough the importance of having someone with Comanche knowledge involved in the pre-buy. Esp when it comes to things like the landing gear.

- Charles

[jeffrey aryan]

David,

I'm no A&P. My only comment would be,

What would it take to repair the condition and to what type of repairs are you talking about ? new stuff ?, just that area ?

Then that should be reflected in the price and that can be negotiated.

Also, living in the Los Angeles or San Diego area is not a major concern about corrosion. There are many planes based along the coast and they get minimal corrosion at worst case.


Jeff Aryan